Dual stage actuation (DSA) disk drive head suspensions are generally known and commercially available. By way of example, one embodiment of a DSA head suspension 10 is shown in FIGS. 1A and 1B. The illustrated DSA suspension includes a baseplate 12, hinge 14 or spring region, load beam 16 and integrated lead flexure 18 with traces 20. The hinge 14 is mounted to the baseplate 12 and extends from the distal end of the baseplate. The load beam is mounted to the distal end of the hinge 14. The flexure 18 is mounted to the load beam 16, typically on the side of the load beam mounted to the hinge 14. Welds such as 22 are typically used to join these components. The baseplate 12, hinge 14 and load beam 16 are typically formed from stainless steel, and the flexure 18 typically includes a base layer of stainless steel. The copper or copper alloy traces 20 on the flexure 18 are separated from the stainless steel base layer by a layer of polyimide or other insulator.
The second stage actuation functionality of the illustrated DSA suspension 10 is incorporated into the baseplate 12. As shown, the baseplate 12 has one or more motor-receiving areas or openings 24 (two in the illustrated embodiment). Piezoelectric (PZT) motors 26 are mounted to the baseplate 12 in the motor-receiving openings 24. The motors 26 are mounted to tabs 28 extending from the baseplate 12 into the motor-receiving openings 24. In the illustrated suspension 10 the tabs 28 are portions of the hinge 14. In other embodiments (not shown) the tabs 28 to which the PZT motors 26 are mounted can be other components such as a separate motor plate welded to the baseplate. Epoxy or other adhesive is typically used to mount the motors 26 to the tabs 28.
DSA suspensions can be embodied in still other forms. For example, an alternative DSA suspension structure is illustrated and described in the Okawara U.S. Patent Publication No. 2010/0067151 which is incorporated herein by reference in its entirety and for all purposes. Briefly, the suspension shown in the Okawara publication has an actuator plate to which the motors are mounted. The actuator plate is mounted between the baseplate and hinge. In still other DSA suspensions (not shown), the motors can be mounted to the load beam or hinge.
An electrical connection or conductive joint between an electrical ground contact on a face of the motor and the ground plane of the suspension is typically made by conductive adhesive (e.g., epoxy with silver and/or nickel particles). The ground contacts on the motors typically have an external plated gold (Au) layer. These connections are typically formed by applying a mass of the conductive adhesive at a location where the ground contact of the motor is adjacent to a stainless steel portion of the baseplate, load beam, hinge or flexure. The conductive adhesive contacts both the motor ground contact and the stainless steel portion of the suspension, thereby providing an electrical connection or ground joint from the motor to the stainless steel portions of the suspension that function as the ground plane.
The conductive joint between the motor and the ground plane should be capable of functioning at or below a threshold level of acceptable resistance under all applied processing and operational load conditions. However, consistently maintaining acceptable resistance to ground levels has been difficult. In particular, the resistance of the conductive adhesive-to-stainless steel component joints have been determined to be relatively high and unstable.